The thickness inspection of thin organic films, such as extruded polymeric sheets, blown-film polyethylene materials or corrosion-protective transparent films and varnish paints on metal, is a problem of great concern for the plastics and rubber industry. The uniformity of the film thickness is important both for economic and for functional reasons. As such films are certified by the manufacturer as having a given minimal thickness, fluctuations above such a minimal thickness should be as small as possible in order to minimize the excess quantity of required raw material. As to the functional reasons, a minimum thickness is required for a given corrosion-protection performance, while exceedingly thick coatings are more subject to interface stresses eventually leading to a loss of adherence to the substrate. Moreover, a departure from a uniform cross-machine-direction thickness profile indicates the presence of a process malfunction such as an eccentricity of the concentric extruding dies in a cylindrical film-blowing machine.